1. Field of the Invention
The present invention relates to a burner for premixing-type combustion of a liquid fuel. It also relates to a method for operating such a burner.
2. Discussion of Background
U.S. Pat. No. 4,932,861 to Keller has disclosed a burner, in the interior of which is placed a fuel nozzle which forms a conical fuel spray which spreads out in the direction of flow. Around the spray combustion air streams flowing in tangentially to the interior of the burner flow and which is broken down as regards the mixture in the direction of flow of the burner. The tangential inlet openings into the interior of the burner are formed by virtue of the fact that the burner itself comprises two hollow conical part-bodies, the center lines of which extend in mutually offset fashion. The ignition of this air/fuel mixture takes place at the outlet of the burner, and in the region of the burner aperture a return flow zone forms which, together with the high axial velocity upstream thereof, prevents the occurrence of a kickback of the flame from the combustion chamber in the upstream direction into the burner.
If diesel oil is used as a fuel for operating a combustion chamber, it has been found that this can ignite immediately after being admixed to the burner. For this reason, it is not always possible to achieve premixing-type operation under relatively high pressure conditions using a liquid fuel. The reason for the large deviations as regards ignition delay time is also connected with the flame radiation: under high pressure, the flame radiation will be very great; a significant portion of the radiation is absorbed by the fuel droplets (opaque mist). This mechanism of the energy transfer to the liquid fuel leads to a drastic reduction in the ignition delay time.